U.S. patent number 5,909,032 [Application Number 08/845,513] was granted by the patent office on 1999-06-01 for apparatus and method for a modular electron beam system for the treatment of surfaces.
This patent grant is currently assigned to American International Technologies, Inc.. Invention is credited to George Wakalopulos.
United States Patent |
5,909,032 |
Wakalopulos |
June 1, 1999 |
**Please see images for:
( Certificate of Correction ) ** |
Apparatus and method for a modular electron beam system for the
treatment of surfaces
Abstract
A modular electron beam device is disclosed, the device being
housed in a modular enclosure containing a power supply subsystem
coupled to provide power to an electron beam tube. The enclosure is
shaped to permit stacking of plural such modular units in a way
that the stripe-shaped beam emitted from each of the units
completely irradiates a surface to be treated. Beams may lie on
different lines but the combined beams sweep out a width on a
surface which is a continuous span. In an alternate embodiment of
the invention, the modular unit comprises a plurality of electron
beam units, each comprising an electron tube and a filament and
bias supply to power the tube. A single high voltage stack is
common to the plural tube/filament/bias sub-units. A daisy-chain
arrangement allows for the single high voltage stack to power all
of the tube units. In yet another embodiment, the modular unit
comprises a plurality of electron tubes powered by a single power
supply.
Inventors: |
Wakalopulos; George (Pacific
Palisades, CA) |
Assignee: |
American International
Technologies, Inc. (Torrance, CA)
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Family
ID: |
25295401 |
Appl.
No.: |
08/845,513 |
Filed: |
April 24, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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369127 |
Jan 5, 1995 |
5612588 |
|
|
|
Current U.S.
Class: |
250/492.3;
313/420 |
Current CPC
Class: |
H01J
5/18 (20130101); B29C 71/04 (20130101); H01J
37/06 (20130101); H01J 33/04 (20130101); H01J
33/00 (20130101); B29L 2007/008 (20130101); H01J
2237/164 (20130101); B29L 2031/3462 (20130101); B29C
2035/0877 (20130101) |
Current International
Class: |
H01J
5/18 (20060101); H01J 33/04 (20060101); H01J
33/00 (20060101); H01J 37/06 (20060101); H01J
5/02 (20060101); H01J 037/30 () |
Field of
Search: |
;313/420
;250/492.3,492.2,400 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Anderson; Bruce
Attorney, Agent or Firm: Schneck; Thomas Yee; George B. F.
McGuire, Jr.; John P.
Parent Case Text
This application is a continuation-in-part of application Ser. No.
08/369,127 filed on Jan. 5, 1995, now U.S. Pat. No. 5,612,588.
Claims
I claim:
1. A modular electron beam apparatus comprising:
a modular housing;
an electron beam tube contained in the housing, the electron beam
tube having an electron emitting end exposed through an opening in
the housing, the electron beam tube further having means for
producing a stripe-shaped beam having a width substantially equal
to a dimension of the housing, and;
a power supply means contained in the housing, coupled to provide
power to the electron beam tube;
the modular housing having a shape to fit together closely in an
interlocking manner with an adjacent second modular apparatus in a
manner such that the stripe-shaped electron beams emitted from both
modular apparatuses together sweep over a region having a
continuous width that is greater than the width of either beam
alone but less than the sum of widths of the two electron
beams.
2. The modular apparatus of claim 1 wherein the modular housing
includes means for coupling to a second modular apparatus, the
modular housing being dimensioned so that a region swept by the
stripe-shaped electron beam is substantially adjacent a region
swept by the stripe-shaped electron beam of the second modular
apparatus.
3. The modular apparatus of claim 1 wherein the modular housing
includes a rectangular member and a cylindrical member attached and
vertically aligned along a first side of the rectangular member,
the electron beam tube being disposed within the cylindrical
member.
4. The modular apparatus of claim 3 wherein the cylindrical member
includes a slotted opening oriented perpendicular to a long axis of
the rectangular member.
5. The modular apparatus of claim 3 wherein the cylindrical member
has a diameter greater than the width of the rectangular member,
whereby a first modular apparatus can be stacked upon a second
modular apparatus such that a stripe-shaped electron beam emitted
from the first modular apparatus sweeps out a zone of irradiation
that is substantially adjacent to a zone of irradiation swept out
by a stripe-shaped electron beam emitted from the second modular
apparatus.
6. The modular apparatus of claim 1 wherein the electron beam tube
comprises a vacuum tube envelope having an aperture at a first end
of the vacuum tube envelope, a base at a second end of the vacuum
tube envelope, and an electron permeable, gas impermeable, low-Z
window covering the aperture through which a beam of electrons is
emitted; the filament includes first electrode ends passing through
the base for electrical connection to the power supply means; the
means for accelerating includes a cathode plate disposed proximate
the filament and further including an anode coupling to the window,
the cathode having second electrode ends passing through the base
for electrical connection to the power supply means.
7. A modular electron beam device comprising:
an enclosure for housing a plurality of electron beam units, the
enclosure having a shape to fit together closely in an interlocking
manner with an adjacent enclosure of a second electron beam
device
each electron beam unit having:
a vacuum tube containing therein a filament and a cathode, the
vacuum tube including a slot-shaped aperture at one end thereof for
emitting the electron beam and further including a window to
provide an airtight seal over the aperture;
a first high voltage terminal coupled to provide a high voltage
source to the electron beam tube;
a second high voltage terminal coupled to the first high voltage
terminal;
a filament power supply electrically coupled to the filament;
and
a bias power supply electrically coupled to the cathode;
the electron beam units being coupled in daisy-chain fashion,
wherein the first high voltage terminal of an electron beam unit is
coupled to the second high voltage terminal of another electron
beam unit.
8. The modular device of claim 7 wherein each of the electron beam
units emits a stripe-shaped beam and the electron beam units are
aligned such that the stripe-shaped beams sweep out a width on a
target surface which is a continuous span.
9. The modular device of claim 8 wherein each of the electron beam
units further includes means for deflecting the electron beam
thereby producing the stripe-shaped beam.
10. The modular device of claim 9 wherein the means for deflecting
is a magnetic yoke externally disposed about the electron beam
unit.
11. The modular device of claim 8 wherein for each of the electron
beam units the filament is an elongated linear filament and the
cathode has a elongated shape, thereby producing the stripe-shaped
beam.
12. The modular device of claim 7 further including a high voltage
power supply coupled to the first high voltage terminal of a first
one of the electron beam units.
13. The modular device of claim 7 wherein the window of each
electron beam unit is a low-Z crystalline membrane which is
permeable to electrons and impermeable to gases.
14. The modular device of claim 7 wherein the enclosure further
houses a feedback circuit for sensing electron beams emitted from
the electron beam units and adjusting the operation of the electron
beam units so that the energies of the emitted electron beams are
substantially equal to each other.
15. An electron beam device comprising:
an enclosure containing therein a plurality of electron beam tubes
adjacent one another and a power supply coupled to provide power to
the electron beam tubes, the enclosure being of a shape to fit
together closely in an interlocking manner with an adjacent
enclosure of a second electron beam device;
each of the electron beam tubes comprising a sealed chamber defined
by a first end and a second end and having a thermionic filament
disposed in the chamber and a cathode disposed proximate the
thermionic filament, the first end of the sealed chamber having a
slot-shaped aperture therethrough and sealed by an electron
permeable member, the thermionic filament and cathode each having
electrodes passing through the second end for electrical coupling
to the power supply;
the electron beam tubes being oriented so that the slot-shaped
apertures are parallel to a longitudinal axis;
the electron beam tubes being staggered so that the slot-shaped
apertures of adjacent pairs of electron beam tubes lie along a
common axis.
16. The electron beam device of claim 15 wherein for each of the
electron beam tubes the electron permeable member is a low-Z
crystalline material.
17. The electron beam device of claim 16 wherein the electron
permeable member includes an anodic connection to provide a
potential gradient between the cathode and the electron permeable
member.
18. The electron beam device of claim 15 wherein each of the
electron beam tubes includes a deflection means for reciprocating a
beam of electrons to produce a stripe-shape beam of electrons.
19. The electron beam device of claim 15 wherein for each of the
electron beam tubes the filament has an elongate linear shape and
the cathode has an elongate shape, thereby producing a
stripe-shaped beam of electrons.
20. The electron beam device of claim 15 wherein each of the
electron beam tubes includes a pair of tuning grids disposed within
the sealed chamber downstream of the thermionic filament, the
tuning grids further disposed in opposed relation to each other so
that an electron beam can pass therebetween, the tuning grids
having an adjustment means coupled to the power supply for creating
a voltage potential therebetween, thereby steering a passing
electron beam; whereby the electron beam of each of the electron
beam tubes can be individually adjusted.
Description
TECHNICAL FIELD OF THE INVENTION
The present invention relates to electron beam devices and in
particular to electron beam devices having a modular design.
BACKGROUND OF THE INVENTION
Electron beam and ultraviolet sources are the primary options for
irradiating surface layers. Existing surface curing systems,
however, are fixed-size configurations and are not easily modified
to accommodate different sized surfaces. Surface curing
applications can involve web sizes ranging anywhere from 1 inch to
60 inches in width. However, because of the inherent
non-scalability of fixed-size surface curing systems, electron beam
treatment has been an impractical and therefore seldom used
option.
The growth of electron beam systems has stalled due to resistance
in a number of areas which challenge the advancement of the
technology. First, there is the high cost of the systems resulting
from the need for scalability in order to accommodate various
surface dimensions. Second, is the overall size of a typical high
energy electron beam system, its so-called footprint, which
typically includes a vacuum sub-system, the power supply and
transformers. A related concern is the need for protective X-ray
shielding in high energy electron beam systems. This results in
added material and physical complexity of the system.
Operationally, there is concern over the issue of surface reaction
rate of the curable material with atmospheric oxygen. This
undesirable interaction of the chemistry with oxygen affects the
chain reaction of the surface, resulting in improperly treated
surfaces. System up-time is another consideration worth noting.
With single-unit electron beam devices, failure of any part of the
device makes the entire system inoperable.
Manufacture of single-unit systems tends to drive up the cost of
these systems. Precise alignment of the individual components
comprising such systems is required and testing of large systems is
a time consuming effort, adding significantly to the cost of
manufacture.
What is needed is an electron beam system suitable for surface
curing applications, which can economically be scaled up to
accommodate high-speed, wide-web curing operations. At the same
time, such a system should have a low specific cost and is compact
to accommodate a wide variety of electron beam applications.
SUMMARY OF THE INVENTION
In accordance with the present invention, a modular electron beam
device includes a modular enclosure housing an electron beam tube
for producing stripe-shaped electron beams which are emitted
through an opening in the enclosure. The enclosure also houses a
power supply for powering the electron beam tube. The modular
enclosure has a shape which can receive another such enclosure in a
manner such that the two electron beams together sweep over a
region that has a width substantially the sum of the widths of such
beams.
In an alternate embodiment, an electron beam device is comprised of
a plurality of electron beam units. Each unit comprises a vacuum
tube element for producing an electron beam with its own filament
and bias supply to provide power to the vacuum tube. In addition,
each electron beam unit includes a pair of high voltage terminals,
allowing the units to be connected in daisy-chain fashion. This
configuration allows for a single high voltage stack to be used to
power the daisy-chained units. A feedback circuit is provided to
monitor each of the beams and to adjust the output of each unit so
that the beams have the same energy level.
The electron beam tubes used in the above embodiments comprise a
vacuum sealed chamber having at one end a filament for producing
electrons and a cathode plate proximate the filament. At a distal
end of the chamber, a slot-shaped aperture permits emission of
electrons from the tube. An electron permeable window provides an
airtight seal over the aperture. The window is coupled to provide
an anodic connection, typically ground potential. In one variation
of the invention, the electron beam tube generates stripe-shaped
beams by electrostatic or magnetic means, such as a magnetic yoke
mounted around the tube operated to cause a beam of electrons to
scan in reciprocating fashion. Alternatively, the filament element
may be an elongate element producing a band of electrons which are
deflected by a similarly elongate parabolic cathode. The resulting
stream of electrons emitted from the tube has a stripe shape to
it.
In yet another embodiment of the present invention, an electron
beam device comprises a plurality of electron beam tubes, each
capable of forming a stripe-shaped beam of electrons. In this
embodiment, a single power supply is used to power each of the
tubes. The tubes are arranged in a staggered format in such a way
that the stripe-shaped beams each is parallel to a given axis, and
pairs of adjacent beams lie along a common axis. The resulting zone
of irradiation swept by the beams is equal to the sum of the width
of each of the beams. Each of the electron beam tubes in this
embodiment additionally includes a pair of tuning grids used to
steer the electron beam and to adjust its intensity.
The modular approach of the present invention provides an easy and
inexpensive upgrade path for scaling up to large surface treatment
applications, simply by combining additional units as needed. In
addition, added flexibility is achieved because the system can be
scaled down when needed, simply by removing unneeded electron beam
modules. System reliability is increased since a failure of one or
more modules can be quickly and inexpensively corrected by
replacing the failed units, allowing the operation to continue
while the failed units are repaired offline.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the present invention.
FIGS. 2A and 2B show the packaging of an electron beam module.
FIG. 3 shows the stacking made possible by the modular design shown
in FIGS. 2A and 2B.
FIG. 4 illustrates zone of irradiation swept out by the arrangement
of the electron beams modules of the present invention.
FIGS. 5A-5C show alternate shapes for the enclosure shown in FIGS.
2A, 2B, and 3.
FIGS. 6A-8B schematically illustrate variations of the electron
beam tube used in the present invention.
FIGS. 9 and 10 show alternate embodiments of the present
invention.
FIG. 11 is a circuit for adjusting the tuning grid illustrated in
FIGS. 6C and 6D.
BEST MODE OF CARRYING OUT THE INVENTION
As shown in the schematic of FIG. 1, the modular electron beam
device of the present invention includes a modular enclosure 10
housing an electron beam tube 20 and a power supply subsystem
comprising a high voltage stack 12, a filament supply 14, and a
bias supply 16. These components are readily available and do not
involve any talent beyond a level of ordinary skill to acquire and
assemble. The components of the power supply subsystem are coupled
to the electron beam tube 20 through a socket 18. The electron beam
tube 20 is configured to emit a stripe-shaped electron beam through
an electron emitting end 21.
In the preferred embodiment of the invention shown in FIGS. 2A and
2B, the modular enclosure 10 consists of a rectangular portion 10a
and a cylindrical portion 10b coupled to a side of the rectangular
portion. The high voltage stack 12 is a high voltage step-up
transformer and so typically will occupy a large portion of the
interior volume of the enclosure. Therefore, it is shown disposed
in the rectangular portion 10a of the enclosure. The filament and
bias supplies 14, 16, being lower voltage and thus smaller devices,
are collocated with the electron beam tube 20 in the cylindrical
portion 10b.
The bottom view of FIG. 2B shows that an opening 10c is formed
through the enclosure, thus exposing the electron emitting end 21
of the electron beam tube 20. The opening 10c is slot-shaped to
coincide with the stripe-shaped beams emitted by the electron beam
tube. As shown in the figure, the long dimension D1 of the slotted
opening 10c is oriented perpendicular relative to the long
dimension D2 of the enclosure 10. The bottom view of FIG. 2B
further shows that the diameter D of the cylindrical portion 10b is
slightly wider than the width W of the rectangular portion 10a. As
will be explained below with reference to FIG. 3, such an enclosure
facilitates stacking together multiple modules.
Turning then to the bottom view of FIG. 3, an arrangement of five
modules 20a-20e is shown in which the modules are stacked together
in accordance with the invention. Each module is stacked adjacent
its neighbor in such a way that the cylindrical portions of
adjacent modules (e.g. 20a and 20b) are distally positioned
relative to each other. The resulting stack of modules resembles
two sets of interlocked fingers when viewed from the top, or the
bottom as in FIG. 3. It can be appreciated from FIG. 3 that the
shape and dimensions of the enclosures 18 result in a desired
alignment of the stripe-shaped electron beams.
FIGS. 3 and 4 show that the stripe-shaped electron beams are
aligned to sweep out a continuous zone of irradiation upon a
surface to be treated. In FIG. 3, the modules are stacked so that
adjacent pairs of such modules share a common axis; e.g. modules
20a and 20b share axis A1, modules 20b and 20c share axis A2, and
so forth. In addition, the cylindrical portions of the modules are
arranged in staggered fashion so that the slotted openings 10c of
adjacent pairs of modules lie along their respective common axes,
more clearly exemplified in FIG. 4.
FIG. 4 shows a surface 100 which is carried beneath a set of
electron beam tubes 20a-20e, shown in phantom, in the direction
indicated. As noted above, the electron tubes emit stripe-shaped
beams 22a-22e which strike the surface being treated 100. As shown
in the figure, each beam irradiates a portion of the surface,
forming strips of irradiation regions 112a-112e on the surface. As
a result of the above-described alignment of the tubes, the
irradiated strips 112a-112e form a continuous swath spanning the
width of the surface 100 being treated. Thus, surfaces of any width
are easily and quickly accommodated simply by adding (or removing)
modules as needed. In practice, some overlap of adjacent
irradiation regions is desired in order to deliver a sufficiently
uniform dose to the surface 100. Preferably, the amount of overlap
will ensure a dose-delivered variance in the range of .+-.5%.
Returning to FIGS. 2 and 3, it is now clear that the specific shape
of the enclosure 10 is not critical. It is necessary that the
enclosure be capable of containing the power subsystem and the
electron beam tube, and that the enclosure have a shape which
permits stacking of plural modules in the manner described above
and shown in FIGS. 3 and 4, namely that the individual
stripe-shaped electron beams sweep out a region of irradiation on
the surface being treated that is as wide as the sum of the width
of the beams. FIGS. 5A-5C show alternative shapes for the enclosure
10. Observe that in each case, the shape of the enclosure permits
the slotted apertures 10c of adjacent modules 20a, 20b to lie along
a common axis A.
Turn now to FIGS. 6A-7B for a discussion of the electron beam tubes
used in the present invention. As illustrated schematically in
FIGS. 6A and 6B, an electron tube 20 comprises a vacuum tube
envelope 50 containing at one end thereof a thermionic filament
member 54 and a cathode plate 56. The power subsystems 12-16 (FIG.
1) are electrically coupled to the filament 54 and the cathode 56
via electrodes 62. At an end of the tube envelope 50 distal to the
cathode/filament pair is a slotted aperture 52. The aperture is
sealed by a window 58 which has an anodic connection, typically to
ground. A desired property of the window 58 is that it is capable
of maintaining a gas-tight seal, yet is permeable to electrons.
Preferably, the window is a thin layer of low-Z material (i.e. low
atomic number material). A more detailed discussion is provided in
U.S. Pat. No. 5,414,267 and U.S. Pat. No. 5,612,588, both assigned
to the assignee of the present invention and incorporated herein by
reference.
In the variation of the electron tube shown in FIG. 6A, a
point-source beam of electrons 23 is produced which must be scanned
to produce the desired stripe-shaped electron beam. This is
accomplished by having a magnetic yoke 60 which deflects the beam
in reciprocating fashion thus producing a stripe-shaped beam.
Alternatively, beam deflection can be achieved through the use of
electrostatic plates, such as the plates 61 shown in FIG. 6B. The
underlying principles of magnetic and electrostatic deflection
techniques and methods are known and well understood, so further
discussion in this area is not necessary.
FIGS. 7A and 7B show an electron tube capable of producing a
stripe-shaped beam without the aid of a deflection element. Such a
tube is more fully described in above-identified U.S. Pat. Nos.
5,414,267 and 5,612,588. Briefly, the tube comprises an elongate
linear filament 54' for producing electrons and a similarly
elongate parabolic-shaped cathode plate 56'. The elongate filament
produces a cloud of electrons which extends the length of the
filament. The electrons are then accelerated by the cathode toward
the anode-connected window 58, thus creating a beam of electrons
having the shape of a stripe. Although the figures show the use of
a thermionic filament 54, 54', an indirectly heated cathode tube
could be substituted for producing electrons.
Refer now to FIG. 9 for a discussion of an alternate embodiment of
the invention. Illustrated is a modular configuration where each
electron beam module 200 comprises an electron beam tube 20 powered
by its own filament supply and bias supply 14, 16. In addition,
each module 200 includes a first and a second high voltage terminal
120, 122, one terminal for connection to a high voltage source and
the other terminal for passing on the high voltage source to
another module. This permits the modules 200 to be coupled in
daisy-chain fashion and powered by a single high voltage source, as
shown in FIG. 9. The modules are stacked in staggered fashion much
like the modules shown in FIG. 3 to provide a continuous band of
radiation across the width of a surface being treated. Additional
modules 200 can be added to the chain to provide wider radiation
coverage of the surface being treated.
The output of each module 200 is monitored by a monitoring means
32, such as an ammeter. This information is fed to controller 30,
which compares the outputs of all the modules 200. The controller
30, typically a computer-based device, then adjusts certain ones of
the modules to vary their output. This feedback mechanism can be
used to equalize the outputs of the modules, providing a uniform
radiation of the surface being treated. Alternatively, the
controller 30 can be programmed to provide a non-uniform
arrangement of beam outputs from the modules for applications which
require such treatment.
FIG. 10 shows yet another embodiment of the invention, illustrating
a modular electron beam device comprising a single power supply 70
coupled to plural electron beam tubes 20a-20e. The supply 70 in
this embodiment includes the high voltage stack, the filament
source and the bias source. Note the staggered stacking arrangement
of the tubes which is shown more clearly in FIG. 4. Additional
tubes can be added to the stack as needed to provide a wider swath
of irradiation on the surface being treated.
Since the electron beam tubes 20a-20e are powered by a common
source 70, each tube must be pre-balanced to produce uniform output
among all of the tubes. There are two aspects of the beam that must
be adjusted to achieve a uniform output: beam intensity and beam
position. FIGS. 8A and 8B show a variation of the electron tube
shown in FIGS. 6A-7B which permits such adjustments. As shown in
FIG. 8A, a split-grid pair 63a, 63b is included in the electron
tube. By applying appropriate potentials at each grid the beam can
be positioned by steering the beam as shown. Similarly, the beam
intensity can controlled by varying the amount of bias applied to
the grid pair. FIG. 11 shows a resistor circuit which permits both
adjustments to be made. The bias supply is coupled through
potentiometer P1 to potentiometers P2 and P3, which in turn are
coupled to grids 63a and 63b respectively. Adjusting potentiometer
P1 varies the amount of voltage bias, thus controlling the
intensity of the beam. Adjusting P2 and P3 separately creates
different voltages on the respective grids 63a, 63b, so that the
electric potential between the grid pair can be varies to the steer
the beam as needed. In the preferred embodiment, the tuning
resistors can be permanently built into the tube socket 18 (FIG. 1)
of each tube.
* * * * *